J. Fetzer, S. Kurz, G. Lehner, and W. Rucker. Proceedings of the 7th International IGTE Symposium on Numerical Field Calculation in Electrical Engineering, page 336-340. Graz, (1996)
A. Buchau, W. Rucker, U. Wössner, and M. Becker. COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, 28 (4):
948-963(July 2009)